1.
Take the two candy cords - assign one colour to represent the pentose sugar
molecules and the other to represent the phosphate molecules. Cut the candy
cords into 2 - 3 centimetre pieces.

2. Using the needle
and thread string half the candy pieces together lengthwise alternating the
two colours to form a chain.

3. Repeat step
2 with the remaining half of candy pieces to form a second chain of the same
length.

4.
Lay the two chains down side by side so pieces of the same colour are opposite
one another.

5. Count the number
of pentose sugar molecules you have in one chain (you should have the same number
in both chains). Obtain this number of cocktail sticks. These represent hydrogen
bonds that hold the base pairs together.

6. Divide
the sweets into four different colours. Assign names to the each of the
four colours to represent the nucleotide bases - adenine, cytosine, guanine
or thymine.

For example:

adenine

thymine

cytosine

guanine

7. The bases
have to be paired up on the cocktail sticks. Adenine always pairs with
thymine and guanine with cytosine, so make sure you get the
right colours matching.

8. Push each
end of a cocktail stick into candy pieces representing pentose sugar molecules
lying opposite one another - the cocktail sticks should join the two chains
together so they look like the rungs of a ladder.

9. Hold the
end of each chain and twist slightly to get the double helix effect for
your DNA model.